A major problem in devices such as the rotary processor shown in the co-pending application of Zehev Tadmor, Ser. No. 795,211, entitled "Method and Apparatus for Processing Polymeric Material", now Pat. No. 4,142,805 filed May 11, 1977, as a continuation-in-part of Application Ser. No. 654,040, filed Feb. 2, 1976and now abandoned, is establishing a seal between a rotary portion of the apparatus and a stationary portion of the apparatus, which will be capable of resisting leakage of liquid from channels of the processor.
Depending upon the process an individual channel in the rotor performs, it might generate high or moderate pressure. The pressure which increases linearly might be distributed along the complete circumference or only along a portion of the circumference or a sequence of pressure rises followed by sharp drops following a mixing element might take place. The processing channel to be sealed might be located between other channels with different pressure profiles around the perimeter receiving material from an upstream channel and discharging it into a downstream channel or discharging the material under relatively high pressure to the outside. The elements located at the ends of a string of channels might either be receiving material and operate at moderate pressure or discharge melt at high pressure. In the case of end channels, prevention of leakage is a very important problem. In the case of intermediate channels, leakage flow is of lesser importance. In applications of the rotary processor where power consumption has to be held at a low level, the power dissipated in the seal is a critical factor in the design of the seal. In other applications where a high power input is essential to achieve certain desired modifications of the state of the polymer, a somewhat higher power consumption in the seal can be tolerated if other advantages can be achieved that way.
Another important problem to be considered in the design of a seal for the rotary processor is the fact that the polymers to be processed in that device are generally degrading as a result of temperature and shear. The designer of seals for other materials (oils), although he might be using similar design elements, is generally not confronted with this problem.